Method of producing paper pulp from fibrous material



Patented Oct. 22, 1935 UNITED STATES unrnon or raonucmc PAPER PULP mommuons m'rnam Edwin P. Jones, Garden City, andJames M. Dempsey, New York,N. Y., assignors to Champagne Paper Corporation, New York, N. Y., acorporation of New York No Drawing. Application April 10, 1935,

-- Serial No. 15,620 a 8 Claims. (01. 92-11) Our present inventionrelates to the manufacture of paper, and the like from. cellulosecontaining materials, and more particularly to an improved method ofpreparing pulp to be used in such manufacture.

Specifically, our present invention relates to'an improved method ofproducing a satisfactory pulp for paper making from crude decorticatedbast fiber, such as flax or hemp, which either has or has not been firstsubjected to the usual and ordinary retting process.

An object of our invention is an improved method 01' producing a betterquality of paper pulp from decorticated flax or hemp than has beenheretofore possible.

Another object of our invention is an improved method of treatingfibrous material, derived from fiax or hemp stalks, to produce a pulphaving strength, color, and other characteristics superior tothatproduced by previously known' methods.

In the previously known'methods of producing paper pulp from fibrousmaterial, derived from flax or hemp stalks, it is the practice tosubject the fibrous material to a chemical treatment for the P pose ofloosening and removing, to a more or less degree, the lignins andincrustants which bind the fibers together, so that the fibers may beeasily separated. After such chemical treatment the separated fibers,are ordinarily subjected to a I bleaching process to increase thewhiteness of the fibers to the desired degree.

Because of the limitations imposed on this bleaching process, it hasbeen necessary to sacri-r fice, to some degree, the'quality of thefinished pulp. This has been true with respect to certain types offibrous material, particularly flax, in

, which a very large proportion of the fibrous material must bedestroyed during processing, if the hard fiber bundles or shives aresufiiciently treated to permit of securing a resulting final Pulp ofsatisfactory whiteness with known bleaching methods.

in our present invention we have departed,

mechanically decorticated flax contains between above described, it isthoroughly washed to re-.

10% and 20% of water-soluble substances, and as a first step in myimproved process we steep the flax tor a short period of time in water.Such period of time mayvary from fifteen to- 30 minutes. I

We find that it is quite immaterial whether hot or cold water isemployed, as the water-soluble substances are dissolved with equalfacility, in either. Cold water is employed however, and we find thatthe same dissolves these water-soluble substancesin a. satisfactorilyshort period of time.

We find further that we can facilitate the subsequent steps of ourimproved method or process by allowing the above referred to steeping in1 water to take place while the fibrous material is 5 being subjected tothe action of a beater, a rod mill, or similar equipment.. Therefore, inpractice, the first step in our improved process consistsin passing themixture of mechanically decorticatedfiax through a continuously operatedequipment (such as heaters, rod mills, etc.) which imparts a crushing,rather than a cutting action to the raw material. 7

After the fibrous 'material has beentreated as move the dissolvedmatter. The fibrous material is then placed in a rotary digester, whereit is cooked at an appropriate temperature and pressure for a,predetermined length of time. The time, temperature, and pressure willvary according to the character of the material being worked upon, butwe have obtained satisfactory results by cooking the material under apressure of approximately 50 pounds per square inch'i'or a period ofapproximately two hours. However, we are of the opinion that theconcentration and combination of chemicals employed in this digestingstep are of more importance than either the temperature, pressure orlength of time of cooking.

We have found that a cooking reagent composed,

-of practically any alkaline chemical in combina- ,actual concentrationof the chemicals expressed Q as pounds of total chemicals in relation tothe total number of pounds of water present yin the' cooking medium isnot critically important, but

is dependent rather upon the ,shape-of the diish cast. An inspection ofthe shives discloses that they have lost a large part of their strengthand have become much softer.

The next, and equally important, part of our improved process or methodcomprises bleachin the shives without at the same time sacrificing thestrength of the bast fiber itself. It-is practically impossible tobleach the cooked conglomerate (that is, bast fiber and shives), usingan alkaline hypochlorite in a single stage bleach, so as to produce asatisfactory pulp. Therefore, we have utilized as this part of theinvention what may be termed a two-stage bleach.

In the first stage bleach the digested conglomerate is treated with apredetermined quantity of either saturated chlorine water orhypochlorous acid or gaseous chlorine. It is ordinarily necessary to useapproximately 23 grams of chlorine for each 100 grams of conglomerate.The amount actually used must of necessity depend upon both the quantityof shives present in the conglomerate, as well as the thoroughness ofthe previously described digestion. The shives absorb or react witheither the chlorine water, gaseous chlorine or hypochlqrous acid,immediately upon exposure to the chemicals mentioned.

In any event, the bast fiber is lightened in color irmnediately and theshivesturn a deep brownishred color, indicating that the chlorine reactsvery quickly upon both the bast fiber andjthe shives.

At the end of about 15 to 30 minutes, depending upon whether or notagitation of the mixture .is employed, practically all of the availablechlorine has been consumed.

The mixture is now washed, either with water or with a mild solution ofany of the common alkalies, such as. sodium hydroxide, sodium carbonate,or the like.

The material is now ready for the second stage of the two-stagebleaching process, which consists in treatment with an alkalinehypochlorite.

The mixture of reddish brown shives and comparatively white bast fiberis placed in'a solution of either sodium or calcium *hypochlorite. Theformer appears to work better than'the common bleaching solution ofcalcium hypochlorite and is to ,be preferred thereto, although goodresults may be obtained with the latter.

The mixture is allowed to remain in the bleaching solution at roomtemperature for approximately seven hours, when it will be found thatthe heretofore small reddish-#brown shives have become practicallywhite, and can hardly be found in the mass of bast fibers which have nowreached a satisfactory color.

To bring about satisfactory bleaching in this stage or the process, wefind it advantageous to use the equivalent of approximately 2-4 poundsof ordinary bleaching powder per 100 pounds of conglomerate. I

After this secondstep of the two-stage bleaching process, the pulp isthoroughly washed to remove all of the bleaching liquor. and the pulp isthen ready to be used in subsequent steps in the making of a highquality 989 The various steps of our process may be varied to suitdifferent conditions, depending largely on the nature of the materialbeing worked upon.

The process may be practiced with the use of apparatus which will permitof the continuous 5 treatment of the fibers from the decorticatin stepto the passing ofthe completely prepared pulp to the paper makingmachine. i

We claim.

1. The improved method of producing vpaper pulp from flax, whichconsists in submitting mechanically decorticated flax to the action ofwater, washing the same, cooking the fibers in a digester in thepresence of an alkaline chemical in combination with a-soluble sulphiteandthen bleaching the fibers. I w

'2. The improved method of producing paper pulp from decorticated fiaxwhich consists in steeping the same in water to dissolve soluble mattercontained therein, washing the same to remove the dissolved matter,cooking in a digester in the presence of an alkaline chemical incombination with a; soluble sulphite, and then bleaching the same.

3. The improved method of producing paper pulp from a conglomerate ofbast fiber and shives, which consistsin steeping the conglomerate inwater, to dissolve the soluble matter contained therein, washing theconglomerate to remove the dissolved matter, cooking the conglomerate ina digester in the presence of an alkaline chemical in combination with asoluble sulphite, washing the conglomerate, and then subjecting theconglomerate to a two-stage bleaching operation.

4. The improved method of 'oducing paper pulp from a conglomerate ofrlber and shives.

chlorine in the presence of water, washing the conglomerate, and thentreating the conglomerate with an alkaline hypochlorite.

' 5. The improved methodof producing paper pulp from a conglomerate ofbast fiber, shives,

' and soluble impurities, which consists in steep.-

ing the conglomerate, to dissolve the soluble impurities, washing theconglomerate to remove the dissolved impurities, milling theconglomerate to crush and soften the shives, cooking the conglomerate ina digester with a reagent composed of approximately 95% sodium carbonateand approximately 5% sodium sulphite, under pressure, washing theconglomerate, treating the conglomerate with a solution of chlorine,washing the conglomerate, then treating the conglomerate with a solutionof sodium hypochlorite for approximately seven hours at roomtemperature, and then washing the conglomerate.

6. The improved method of producing paper pulp from a conglomerate ofbest fiber, shives, and soluble impurities. which consists 'in steepingthe conglomerate, milling the conglomerate, cooking the conglomerate ina digester with a reagent composed of approximately 95% ofsodiumhydroxide and approximately 5% of sodium sulphite under a pressureof'from 30-75-pounds per square inch: treating -the conglomerate withchlorine in the presence of water, and treatin being thoroughly washedbetween each step 01' the method.

'7. The improved method of producing paper pulp from a conglomerate ofbest fiber and shives, which consists in steeping the conglomerate, todissolve soluble matter contained therein, washing the conglomerate toremove the dissolved matter, cooking the conglomerate in a digester inthe presence of an alkaline chemical in combination with a solublesulphite, washing the conglomerate, milling the conglomerate to crushand soften the shives, treating the conglomerate with chlorine in thepresence oi water, washing the conglomerate, and then treating theconglomerate with an alkaline hypochlorite.

8. The improved method of producing paper pulp from a conglomerate ofbast fiber, shlves, and soluble impurities, which consists in steepingthe conglomerate, to dissolve the soluble impurities, washing theconglomerate to remove the dissolved impurities, milling theconglomerate to crush and soften the shives, cooking the conglomerate ina. digester under pressure with a reagent composed 0i? a mixture ofcalcium hydroxide, sodium carbonate and sodium hydroxide in combinationwith sodium sulphite, and-with the mixture constituting approximately95% of the combination, washing the conglomerate, treating 10 theconglomerate with a solution of chlorine,

washing the conglomerate, then treating the conglomerate with a solutionof sodium hypochlorite for approximately seven hours at roomtemperature, and then washing the conglomerate. l6

nnwm 1 JONES. JAMES M. DEMPSEY.

